Babies sleeping with half-open eyes may be caused by factors such as too narrow upper eyelid, too young age and fright. 1. Upper eyelid is too narrow: some babies will have narrow upper eyelids and incomplete lid closure due to abnormal development after birth, thus showing half-open eyes during sleep. 2. Young age: the nervous system and muscles are not yet fully developed, the orbicularis oculi and levator palpebralis muscles, which control the opening and closing of the eyes, are poorly coordinated, which can easily cause children to sleep with their eyes half-open. As the child grows older, the symptoms of half-open-eye sleep will gradually improve as the nerves and muscles become more coordinated. 3. Scaring: If the child is frightened during the day and the central nervous system is hyperactive at night, he or she may also sleep with eyes half open. It is recommended that patients whose babies sleep with half-open eyes and are accompanied by other discomforts should consult a doctor in time to assess their condition and follow the doctor’s instructions for treatment.